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Abstract:

This present invention provides coating compositions that may at least
partially block tannin migration and methods of blocking tannin
migration. Specifically, the coating composition comprises at least one
resin binder, and at least one vinyl pyrrolidone based polymer or
copolymer, or a combination thereof. The coating compositions described
herein at least partially block tannin migration.

Claims:

1. A coating composition comprising:a) at least one resin binder,b) at
least one vinyl pyrrolidone based polymer or copolymer, or a combination
thereof, andwherein the coating composition at least partially blocks
tannin migration.

2. The composition of claim 1, wherein the resin binder is waterborne.

14. A method of at least partially blocking tannin migration comprising
the step of:applying a coating composition to a substrate, wherein the
coating composition comprises at least one resin binder and at least one
vinyl pyrrolidone based polymer or copolymer or a combination thereof.

15. The method of claim 14, wherein the substrate is a tannin-containing
substrate or tannin-stained substrate.

16. The method of claim 14, the coating composition is applied as a
primer.

17. A coated substrate comprising:a) a tannin-containing substrate or
tannin-stained substrate,b) a coating on said substrate comprising at
least one resin binder and at least one vinyl pyrrolidone based polymer
or copolymer or a combination thereof,wherein said coating can at least
partially block the migration of tannin from the substrate.

18. The coated substrate of claim 17, wherein said substrate is a
tannin-containing substrate.

19. The coated substrate of claim 18, wherein said tannin-containing
substrate is selected from the group consisting of wood, paper,
cardboard, plywood, particle board, chip board and strand board.

20. The coated substrate of claim 19, wherein said wood is selected from
the group consisting of redwood, dark wood, cedar, white pine, yellow
pine and oak.

21. The coated substrate of claim 19, wherein said wood is selected from
the group consisting of redwood, cedar, and oak.

Description:

RELATED APPLICATIONS

[0001]This application claims the benefit under 35 U.S.C. §119(e) of
U.S. Provisional Patent Application Ser. No. 61/091,550; Filed Aug. 25,
2008, the disclosures of which is incorporated herein by reference in its
entirety.

[0003]In architectural coatings, a primer is usually applied to a
substrate to provide a foundation for a durable topcoat. When the primer
is applied to a stained substrate, the primer should also have effective
stain blocking properties. Common examples of stains include inks,
crayons, pen markers, and stains caused by water or smoke damage. Another
type of stain is tannin which is abundantly present in cedar, redwood and
other dark woods. Tannins are complex acidic compounds that are observed
as yellow to brown. They are soluble in water and may bleed from
unpainted wood and cause discoloration when a waterborne coating, such as
paint, primer or varnish, is applied to the wood. In addition, tannins
may inhibit curing of waterborne alkyds. Therefore, it is particularly
important to block the migration of tannins when using waterborne alkyd
based coatings.

[0004]Traditionally, solvent borne stain blocking coatings have been used
to block a broad range of stains since most of the stains and the tannins
are insoluble in the solvent carriers of the coating systems. However,
due to the environmental concerns, restrictions have been imposed on
volatile organic compounds (VOC) in such coating systems. In response to
the regulations, it is desired to replace solvent borne coating systems
with waterborne coating systems. However, since tannin is water soluble,
waterborne coating systems are often ineffective at blocking tannin
migration.

[0008]In one embodiment, the molecular weight of the vinyl pyrrolidone
based polymer or copolymer is in the range of about 1000 to about
1,000,000 Daltons. In some embodiments, the ethylenically unsaturated
compound is selected from ethylene, propylene, acrylates, methacrylates,
vinyl acetate, styrene, vinyl toluene and ethylene chloride. In another
embodiment, the weight ratio of the resin binder to vinyl pyrrolidone
based polymer or copolymer is in the range of about 25/75 to about 99/1
mass units.

[0009]The present invention also provides methods of blocking tannin
migration which comprises the step of: applying the coating composition
to a stained substrate. The coating composition comprises at least one
resin binder and at least one vinyl pyrrolidone based polymer or
copolymer or a combination thereof. In some embodiments, the stained
substrate is a tannin-stained substrate or a tannin-containing substrate.

[0010]Another aspect of the present invention provides coated substrates
comprising: a tannin-stained substrate or tannin-containing substrate
(e.g. high tannin content wood), and a coating on said substrate
comprising at least one resin binder and at least one vinyl pyrrolidone
based polymer or copolymer or a combination thereof, wherein said coating
may at least partially block the migration of tannin from the substrate.
In some embodiments, the stained substrate is a tannin-stained substrate
or a tannin-containing substrate (e.g. high tannin content wood).

[0011]One aspect of the present invention provides, in waterborne coating
composition, wherein the improvement comprises an effective amount of at
least one vinyl pyrrolidone based polymer or copolymer or a combination
thereof to at least partially block tannin migration.

DETAILED DESCRIPTION

[0012]The foregoing and other aspects of the present invention will now be
described in more detail with respect to the description and
methodologies provided herein. It should be appreciated that the
invention can be embodied in different forms and should not be construed
as limited to the embodiments set forth herein. Rather, these embodiments
are provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in the art.

[0013]The terminology used in the description of the invention herein is
for the purpose of describing particular embodiments only and is not
intended to be limiting of the invention. As used in the description of
the embodiments of the invention and the appended claims, the singular
forms "a", "an" and "the" are intended to include the plural forms as
well, unless the context clearly indicates otherwise. Also, as used
herein, "and/or" refers to and encompasses any and all possible
combinations of one or more of the associated listed items. Furthermore,
the term "about," as used herein when referring to a measurable value
such as an amount of a compound, dose, time, temperature, and the like,
is meant to encompass variations of 20%, 10%, 5%, 1%, 0.5%, or even 0.1%
of the specified amount. Unless otherwise defined, all terms, including
technical and scientific terms used in the description, have the same
meaning as commonly understood by one of ordinary skill in the art to
which this invention belongs.

[0014]All patents, patent applications and publications referred to herein
are incorporated by reference in their entirety. In case of a conflict in
terminology, the present specification is controlling.

[0015]As used herein, the term "waterborne" means that the solvent or
carrier fluid for the coating composition primarily comprises water. For
example, in certain embodiments, the carrier fluid is at least about 30
weight percent water.

[0017]The present invention provides coating compositions comprising at
least one resin binder, and at least one vinyl pyrrolidone based polymer
or copolymer, or a combination thereof. The coating compositions
described herein at least partially block tannin migration.

[0018]Another aspect of the present invention also provides a coating
composition, wherein the improvement comprises an effective amount of at
least one vinyl pyrrolidone based polymer or copolymer or a combination
thereof to at least partially block tannin migration.

[0019]In some embodiments, the resin binder may be waterborne. In other
embodiments, the resin binder may be selected from acrylic latex, vinyl
acetate/acrylic latex, vinyl acetate/ethylene latex, styrene/acrylic
latex, styrene/butadiene latex, natural rubber latex, alkyd latex,
alkyd/acrylic hybrid resins and water reducible alkyds. In one
embodiment, the resin binder may be alkyd latex. In another embodiment,
the resin binder may be acrylic latex, styrene/acrylic latex or a
combination thereof.

[0020]In some embodiments, the molecular weight of the vinyl pyrrolidone
based polymer or copolymer may be in the range of about 1000 to about
1,000,000 Daltons. In some embodiments, the average molecular weight of
the vinyl pyrrolidone based polymer or copolymer may be in the range of
about 20,000 Daltons to about 150,000 Daltons.

[0021]In another embodiment, if the vinyl pyrrolidone monomer is
copolymerized, the other monomer may be an ethylenically unsaturated
compound. The ethylenically unsaturated compound may be selected from
ethylene, propylene, acrylates, methacrylates, vinyl acetate, styrene,
vinyl toluene and ethylene chloride. In one embodiment, the ethylenically
unsaturated compound may be vinyl acetate.

[0022]The monomer composition of "vinyl pyrrolidone based polymer" is
about 100% vinyl pyrrolidone. The monomer composition of "copolymers of
vinyl pyrrolidone" has about 1% to about 99% vinyl pyrrolidone monomer
content and about 99% to about 1% of the other monomer of the copolymer.
In some embodiments, the copolymer compositions contain about 40% to
about 99% vinyl pyrrolidone monomer.

[0023]The vinyl pyrrolidone based polymers or copolymers of the present
invention may be prepared by any process known in the art, for example
the process described in U.S. Pat. No. 4,786,699. An exemplary vinyl
pyrrolidone based polymer is about 55,000 Dalton homopolymer available
from available from Sigma-Aldrich Corporation, catalogue #856568 (2006
catalogue)

[0024]In some embodiments, the weight ratio of the resin binder to vinyl
pyrrolidone based polymer or copolymer is in the range of about 25/75 to
about 99/1 mass units. In some embodiments, the ratios are about 70/30 to
about 95/5 of resin binder to vinyl pyrrolidone polymer or copolymer. In
one embodiment, the weight ratio of resin binder to vinyl pyrrolidone
based polymer or copolymer is in the range of about 80/20 to about 95/5.
In some embodiments, the weight ratio of resin binder to vinyl
pyrrolidone based polymer or copolymer is in the range of about 90/10.

[0025]In other embodiments, the coating composition may optionally
comprise additives such as pigment, extenders, rheology modifiers,
cosolvents, coalescents, wetting agents, flow/leveling agents, viscosity
controlling agents, pH controlling agents, slip resistant agents, mar
resistant agents, UV stabilizers, catalysts, drier metals biocides and/or
any other adjuvants that are commonly used in waterborne coatings, the
selection of which will be within the skill and knowledge of one skilled
in the art.

[0026]The present invention also provides a method of at least partially
blocking stain migration comprising the step of applying a coating
composition to a tannin-stained or tannin-containing substrate, wherein
the coating compositions comprise at least one resin binder and at least
one vinyl pyrrolidone based polymer or copolymer or a combination
thereof. In one embodiment, the substrate is stained with tannin. In
other embodiments, the coating composition is applied as a primer.

[0027]Another aspect of the present invention provides a coated substrate
comprising: a tanning-containing substrate or tannin-stained substrate;
and a coating on said substrate containing at least one resin binder and
at least one vinyl pyrrolidone based polymer or copolymer or a
combination thereof, wherein said coating can at least partially block
the migration of the tannin from the substrate. In one embodiment, the
substrate is a tanning-containing substrate. In other embodiments, the
tannin-stained substrate is selected from wood, paper, cardboard,
plywood, particle board, chip board and strand board. Yet, in another
embodiment, the substrate is selected from redwood, cedar, white pine,
dark wood, yellow pine and oak.

[0028]The following non-limiting examples are provided to further
illustrate the coating compositions prepared according to the present
invention and used for at least partially blocking tannin migration.

EXAMPLES

I. Examples of Coatings

[0029]Coatings for examples 1-7 were made by using manufacturing
methodologies and appropriate raw materials in ratios known to those
skilled in the art. These exemplary coatings employ the same pigmentation
and pigment volume concentration and are otherwise similar, varying only
in the choice of defoamers and coalescing solvents as demanded by the
specific polymer.

[0032]Items 1 and 2 are mixed for 5 minutes in a vessel equipped with a
high shear "Cowles" blade. Item 3 is added to affect dissolution of item
2. Items 4-6 are added and mixed 5 minutes. Items 7 and 8 are added, the
blade speed is increased and the mixer is run for about 10 minutes to
completely disperse the pigment.

[0033]For examples 1-3, item 9 is added to a mixer. Items 12-14 and
premixed and added to item 9. Items 15-24, as used in these examples, are
added in order. The pigment dispersion, items 1-8, is added. Finally,
item 25 is added slowly and as needed to reach the desired paint
viscosity.

[0034]For examples 4-7, item 10 or 11 is added to a mixer. Items 15-24, as
used in these examples, are added in order. The pigment dispersion, items
1-8, is added. Finally, item 25 is added slowly and as needed to reach
the desired paint viscosity.

IV. Tannin Migration (Bleed) Resistance Test

[0035]Coatings from examples 1-7 were tested as a primer coating for their
ability to prevent tannin bleed or migration. These coatings were brush
applied to rough cut cedar shakes at a spread rate of 300 square feet per
gallon and allowed to air dry. Initial color readings were obtained
instrumentally. A white acrylic latex topcoat, Valspar Ultra Premium
Interior/Exterior High Gloss Enamel, was applied at a spread rate of 400
square feet per gallon and allowed to air dry. Color readings were
obtained instrumentally. Color readings are reported as Yellowness Index
(YI) with the yellowness index being calculated per ASTM D 1925. Color
between coatings is compared per ASTM D 2244-85.

[0036]A water-borne control paint was used in this testing. Kilz 2 from
Masterchem is a latex interior/exterior water-based primer with a label
description as a Multi-Purpose Stain Blocking Formula and available at
hardware and paint stores. Application and color readings were done in
the same fashion as used for Examples 1-7.

[0038]Yellowness Index converts color values from a 3 value, 3 dimensional
scale to a convenient single number. The yellow-brown staining induced by
tannin migration into a primer and/or topcoat results in a higher YI
value compared to a non-stained coating. A difference in YI value of 0.75
is visually significant. Comparing the primer YI values clearly
demonstrates the advantage of adding either vinyl pyrrolidone polymer or
copolymer to alkyd emulsion, styrene acrylic emulsion or acrylic
emulsion. The YI is much lower for primers containing these additive
polymers. The degree of improvement is as much as 2.08 YI units for
Example 6 and 7, and at least 1.30 YI units as seen in Example 1 and 2.
Both the vinyl pyrrolidone polymer and copolymer at least partially block
the migration of tannin into the primer.

[0040]The much lower YI values recorded for topcoats applied over primers
containing either vinyl pyrrolidone polymer or copolymer shows that these
products may bind tannin in the primer and prevent migration into the
topcoat. This is seen for all classes of test polymer, alkyd emulsion,
styrene acrylic latex and pure acrylic latex. The difference in YI seen
is, at a minimum, 0.9 YI units for Examples 4 and 5, visually
significant, and as much as 2.31 YI units for Examples 1 and 3. Further,
the presence of vinyl pyrrolidone polymer or copolymer used in alkyd
emulsion polymers provides a topcoat color superior to that of the
commercial Kilz 2 primer.

VII. Accelerated Testing of Tannin Migration Resistance

[0041]An accelerated test method for tannin migration resistance is
described in ASTM D 6686-01. The painted surface of these cedar panels
was exposed for 16 hours to 100 degrees F. at 100% relative humidity.
These conditions are known to extract tannin from the substrate cedar and
through coatings not designed to block tannin migration. This procedure
was employed for the panels prepared from Examples 1-7 and the commercial
control. Following this exposure, color readings were taken. The YI value
for these primers/topcoats is reported in the table below.

[0043]The much lower YI values recorded for top coats applied over primers
containing either vinyl pyrrolidone polymer or copolymer shows that these
products may bind tannin firmly in the primer and thus, block tannin
migration into the topcoat. This is seen for all classes of test polymer,
alkyd emulsion, styrene/acrylic latex and pure acrylic latex. This test
indicates that the coating composition comprising vinyl pyrrolidone
polymer or copolymer may at least partially block the migration of
tannins from substrate into topcoats in long-term use.

[0044]The foregoing is illustrative of the present invention and is not to
be construed as limiting thereof. Although a few exemplary embodiments of
this invention have been described, those skilled in the art will readily
appreciate that many modifications are possible in the exemplary
embodiments without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such modifications are
intended to be included within the scope of this invention as defined in
the claims. Therefore, it is to be understood that the foregoing is
illustrative of the present invention and is not to be construed as
limited to the specific embodiments disclosed, and that modifications to
the disclosed embodiments, as well as other embodiments, are intended to
be included within the scope of the appended claims. The invention is
defined by the following claims, with equivalents of the claims to be
included therein.